The present invention relates to apparatus for, and a method of, constructing a tunnel, gallery or the like, hereinafter collectively referred to as a tunnel.
Various forms of apparatus are known for constructing tunnels underground. One form of apparatus, with which the invention is mainly concerned, employs a drive or cutting shield composed of elongate members or planks supported in side-by-side relationship around the tunnel so as to contact the wall thereof at least over the roof and side zones. These members are mounted on a rigid frame and are moved, usually by hydraulic rams, to attack a working face. As the tunnel driving progresses the frame is moved up to follow the advanced members. In other constructions the drive shield is in the form of a continuous cylinder advanced by rams rather than separate members. Hitherto various methods have been employed to support the tunnel wall behind the drive shield or its frame. One method which is often employed is to install pre-fabricated lining sections end-to-end as the driving progresses. Although this method is quite successful, the tunnel wall exposed by the shifting of the frame usually remains unsupported for some time until the appropriate lining sections can be placed in position. To overcome this problem other systems have been adopted which employ some form of temporary support for the exposed tunnel wall. However, this necessitates extra equipment and often involves a considerable extension in the overall length of the apparatus and this in turn creates additional problems particularly in that the overall progress of constructing the tunnel may be slowed down. Another problem frequently encountered with the generally known form of apparatus is that the control or guidance of the drive shield is difficult and there is a tendency for the shield to rotate about its axis. Another problem also encountered is that efficient drainage of water is sometimes difficult to achieve without recourse to pumping equipment which is undesirable in the cramped conditions prevailing.
With regard to the foregoing, a general object of the invention is to provide an improved apparatus for, and method of, constructing a tunnel.